Feed pipe location

Effect of feed pipe location (for antisolvent and reactive crystallizations) (see Section 6.6.1.5 below). 

The critical feed time t it depends on the location and number of feed pipes, stirrer type, and mixing intensity, and increases with increasing reactor volume. When a constant power-to-volume ratio is preserved, ta-u is proportional to and where D., is the stirrer diameter and Vr the reactor volume (Bourne and Hilber, 1990 Bourne and Thoma, 1991). The productivity of the reactor expressed as the amount of product formed per unit time becomes almost independent of reactor volume. The reason is that the reaction goes to completion in the zone nearby the stirrer tip. The size of this zone increases independently of the tank size it only depends on the velocity of the liquid being injected, the location of the nozzle, and the stirrer geometry and speed of rotation. Accordingly, for rapid reactions, the feed time will also be the reaction time. 

The feed should be introduced into zones of the highest turbulence, i.e. near the tip of the stirrer at the plane of the agitator or slightly above this plane the velocity of injected reactants should prevent backmixing of the reaction mixture into the feed pipe if the addition time will be too long, consider a multi-injection system with nozzles located at different angular positions. 

FIGURE 2.2 Typical arrangement of feed pipe to reactor vessel and location of inlet boundaries. 

The stagnation point formed by the two impinging jets is located near the end of ethylene and HCl feed pipe. Particle streak lines calculated based on the predicted flow results (not shown in the figure) clearly indicate the location of the stagnation point. 

Translating batch data for continuous reactors In most cases, laboratory-and bench-scale experiments required to validate the reactor concept are carried out in batch mode. It is then necessary to translate (or to use) the data obtained in these experiments to design continuous reactors. The location of feed pipes, outlets and their influence on mixing and performance needs to be understood. Computational flow models can be of great help in this regard. 

Feed pipes are located at impeller center plane... 

If a pressure reducing valve in the feed pipe cannot be avoided, it should be located as far upstream of the vessel as practicable. 

It is preferable to locate large internal liquid feed pipes below the trusses of the next higher tray. 

When the inlet pipe directly feeds the distributor, the incoming liquid should be fed into the center of the distributor in order to ensure uniform head over all the orifices (111, 305). The feed pipe should be located about 2 to 8 in above the top edge of the distributor pan (305). It is important to ensure the feed flows into the distributor and does not enter the vapor risers. In one case (150a) poor column separation resulted from distributor feed being directly introduced into an open riser. 

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